The invention relates to a method and a system for determining the seat climate on seat cushions.
In the development of seats, especially vehicle seats, the main issue is good sitting comfort because the occupants and especially the driver sometimes have to remain seated on vehicle seats for many hours with only limited movement. In this regard, questions of optimum seat pressure distribution and optimum seat climate play a role.
One very important criterion in the development of new vehicle seats or the evaluation of existing seats is their behavior regarding absorption of the moisture produced during prolonged sitting in the form of body perspiration. The climate behavior of a seat is determined by a number of factors, for example the material quality of the covering material, the nature and construction of the multi-layer combination of the covering material, the nature and form of the finishing of the seat covering, the material, nature, and structure of the seat foundation, and the like. If a seat cushion behaves poorly from the sitting climate standpoint, it cannot absorb the moisture given off by a person during prolonged sitting and conduct it into the environment. This produces a damp micro-climate between the person and the seat that is perceived as unpleasant.
In the course of seat development, various seat and cushion designs are prepared as trial samples and these must be compared with one another in an objective and reproducible fashion regarding various testing and evaluation criteria, especially as regards seat climate, in order to be able to pick the best trial sample in this way. Not only new trial samples from actual seat development but also various test seats from other sources, for example seats of earlier seat generations, used seats, or seats from outside development or manufacturing facilities, are compared with one another.
In the publication entitled SAE 1993 Transactions, Journal of Passenger Car, Section 6, Volume 102, pp. 136 to 141, an article by J. Temming was published entitled "A New Method to Assess the Summer Suitability of Car Seats." The article describes a method for spot measurement of the seat climate of vehicle seats. The middle of the seat surface is mechanically and uniformly loaded by a weight over a flat rectangular area of about 15.times.25 cm. The contact area of the test body can be heated to a human body temperature. By means of an interposed specifically moistened fleece, a certain amount of moisture can be added to the area in contact with the seat cushion. By heating this fleece to about 37.degree. C., a specific moisture flow into the seat cushion is produced. By means of moisture sensors located in the contact zone, moisture stagnation on the seat surface can be determined and is intended to be a measure of the seat climate. The disadvantages of the known method include unrealistic sitting pressure distribution during climate measurement due to the cushion being loaded by a body that is rigid and flat in the contact zone. Another disadvantage is the limitation of measurement to a portion of the area located in the middle of the seat on the cushion; to a certain extent, only spot air conditioning is performed.
Experience with the measuring method according to the present invention has shown that the nature and area of cushion loading, and the type of cushion deformation, are very important parameters in the results of a seat climate measurement. With a pressure distribution that corresponds to the previously known measurement method, reproducible and especially informative, i.e. representative, seat climate measured values cannot be expected during measurement in and/or with limitation to a small partial area of the seat, according to experience with the invention. At best, only seats of the same kind can be compared as regards seat climate properties by using the known measurement method or the measured values obtained therewith, and then only with considerable limitations. Comparisons with measured climate values obtained using the known method for different kinds of seats cannot be compared with one another.
On the basis of this prior art, the goal of the present invention consists in further developing the measurement method and the measuring system for seat climate measurement in such fashion that the resultant measured values for seat climate are realistic, reproducible, and representative of the subjectively perceived seat climate for all possible test seats.
This goal is achieved according to the invention by a method for determining the seat climate of a seat cushion of a vehicle seat, in which the seat area is subjected to a moisture flow from a climate mat during realistic mechanical loading of the seat cushion to be tested. Any moisture stagnation at the seat surface is measured. The realistic loading of the seat surface of the seat cushion to be tested is accomplished with respect to total compressive force and sitting pressure distribution in the same way as when a person sits down, by means of an anthropomorphically simulated seat testing punch. The release of the moisture flow from the flexible climate mat interposed in the application area of the seat testing punch against the seat surface also takes place in the direction of the seat surface in such fashion that a quantity of moisture stored in the climate mat in a storage fleece, which is constant for each measurement, is slowly released into the seat surface by heating the climate mat approximately to body temperature.
A measuring system according to the invention is used to determine the seat climate of a seat cushion, especially for practicing the above-method. In the system, the seat cushion to be tested, received in a specific position in a testing machine and covered at the seat surface by a flexible climate mat, is loaded by means of a rigid seat testing punch that anthropomorphically and realistically simulates the area of the buttocks and thighs with regard to bones and soft parts in terms of the total compressive force and sitting pressure distribution as if a person were sitting down. The multilayer climate mat consists of a cover Layer, a storage fleece that stores moisture, a vapor barrier, and an adjustable heating mat, with the cover layer facing the seat cushion and the heating pad facing the seat testing punch during use. The climate mat is made openable between the cover layer and the vapor barrier and between the heating pad for replacement of the storage fleece. At least one flat moisture sensor with signal leads extending outward is located at an especially significant location between the seat surface and the climate mat.
According to the present invention, the seat surface, during a realistic mechanical loading of the seat cushion to be tested, is subjected to a small moisture flow from a climate mat corresponding to a natural sweating process, and any stagnation of moisture at the seat surface is measured.
The less the residual moisture, the better the seat cushion behaves in terms of seat climate. The seat surface of the seat cushion to be tested is loaded realistically in terms of total compressive force and sitting pressure distribution in the same way as when a person sits, using an anthropomorphically simulated seat testing punch. The required moisture flow from the flexible climate mat interposed in the application area of the seat test punch against the seat surface and facing the seat surface is produced by virtue of the fact that moisture is stored in a fleece in the climate mat and released as a result of heating approximately to body temperature.
The following advantages can be achieved by the present invention: (1) the tests proceed under precisely defined measurement conditions; (2) reproducible measurement results are obtained; (3) the measurement results from different seats can easily be compared with one another; (4) the measurements and/or tests can be conducted in a laboratory or in the test garage, i.e. it is not necessary to install the seat in the car; (5) test personnel are spared; (6) the measurement and/or testing of a seat itself requires only half the time in comparison with tests using test subjects; and (7) series measurements are possible without difficulty.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.